The present invention relates generally to cameras and more specifically to a mounting system whereby an interchangeable lens assembly may be mounted and dismounted to and from operative position on the camera. More specifically, the invention relates to a lens mounting system involving bayonent mechanisms including bayonet coupling means on the lens assembly and complementary bayonet coupling means on the camera which are brought to engaged and disengaged positions during mounting and dismounting of the lens assembly.
A bayonet device which is used for mounting a lens assembly on a camera is usually arranged to effect coupling of the relative bayonet devices on the lens assembly and on the camera by interlocking engagement of claws of each of the bayonet members of the lens assembly and of the camera. Usually, the claws of the lens assembly are introduced into cutaway parts located between the claws of the complementary bayonet coupling means on the camera with rotation of the lens claws causing them to be brought behind the inner side of the claws on the camera bayonet mechanism for interlocking engagement. Thus, the lens assembly may be tightly mounted by appropriate rotation of the lens assembly bayonet coupling mechanism while it is in proper position relative to the complementary camera bayonet coupling means.
Generally, the bayonet members involved are provided with two to four or more claws and a corresponding number of cutaway parts. The optical axis of the lens barrel and the optical axis of the camera are brought into coinciding relationship with each other by mating of the claw and cutaway parts of the lens assembly bayonet mechanism with those of the complementary bayonet mechanism on the camera.
Furthermore, a lens assembly and a bayonet mechanism of a camera are generally provided with referenced positioning parts which indicate the correct mounting position of the lens assembly relative to the camera in order to insure that signal transmission members of the lens assembly and complementary parts of the camera which must be brought into engagement therewith will be accurately related with each other so that exposure control signals will be accurately transmitted between the camera and the lens assembly. In mounting the lens assembly on the camera, certain mounting faces of the various parts must be maintained parallel with each other. However, it will be found that due to looseness or inaccuracy of the dimensions of the bayonet coupling means of the lens assembly and of the camera, misaligned mounting may occur. For example, it may be possible to effect misaligned mounting of the lens assembly with the lens axis tilted relative to the camera axis. This, of course, may cause damage to the claws of the bayonet mechanism in that excessive force may result in bending of the parts. Further, the probability of misaligned bayonet coupling of conventional bayonet devices is difficult to eliminate even when a mounting device such as that of the type disclosed in U.S. Pat. No. 3,906,534 is used. This type of mounting device is known as a spigot bayonet mount but it has nevertheless been found to provide less than acceptable results.
Accordingly, it is an object of the present invention to provide a safety mechanism for a bayonet coupling device of a camera which insures that an interchangeable lens assembly will be mounted in correct position on the camera.
It is another object of the invention to provide a safety mechanism for a bayonet device which will protect the bayonet device from being damaged by incorrect mounting action of the interchangeable lens upon the camera.
A further object of the invention is to provide a bayonet device for an interchangeable lens assembly which will insure correct mounting of the lens upon the camera in order to permit accurate transmission of exposure information therebetween.